Evolution and humans: big brain size uses energy (Evolution)

by dhw, Wednesday, November 08, 2017, 13:09 (439 days ago)@ David Turell

DAVID: Obviously to prepare the way for Lucy.
dhw: And why do you think your always purposeful God, who is in full control, needed to change one lumbar vertebra which, according to you served no purpose whatsoever, so that 20 million years later he would be able to make much bigger changes to Lucy?
DAVID: This is the one example I've found. Lucy's anatomy is so different many changes are required. The fossils don't provide them.

So how on earth does that prove that your God changed one lumbar vertebra 23 million years ago in order to prepare the way for Lucy 20 million years later (in order to prepare the way for Homo sapiens)?

dhw: Why do you think every species of ape should have turned into humans? They have managed perfectly well as apes (at least till we came along), or they would have died out. Common descent means all species have branched out from earlier forms. It doesn’t mean every other form had to go extinct or to change into an ape and then into a human.
DAVID: Of course common descent means branching. I'm raising the issue of why this branch appeared at all. We see no driving force, but I see purpose in the giant brain.
dhw: Same old story. Why did ANY branch of ANY species other than bacteria appear at all? What do you reckon was the driving force behind the appearance of the duckbilled platypus?
DAVID: I see no driving force in environmental challenges, but I see a force in God.

Challenges and opportunities. You cannot see that if food was scarce on land, organisms might be forced to seek it in nearby water, or if trees disappeared, tree-dwelling organisms might be forced to spend more time on the land, and such changes might lead to changes in the anatomy? Meanwhile, do you really believe that God was "driven" to specially preprogramme or dabble eight pre-whales, the weaverbird’s nest, the skull-shrinking shrew because it was the only way to keep life going until he could produce the brain of Homo sapiens?

DAVID: You have again equating epigenetic change with full speciation.
dhw: Once again: if brains can rewire themselves, why can't they expand themselves? I never “equate” epigenetic change with full speciation, of which nobody knows the cause. But epigenetic change proves the existence of an autonomous mechanism which may also be responsible for full speciation. (In any case, a hominin with a bigger brain is still a hominin, not a totally new form of being.)
DAVID: Once again you are stretching epigenetic adaptations into an explanation for speciation. It is not, as it only describes adaptation. As for hominins, each stage is a new species, isn't it, requiring the process of speciation?!

I am proposing a hypothesis to explain speciation. We know there is an autonomous mechanism for minor change, but we don’t know if it is capable of major change. (But it is sometimes difficult to draw a line between adaptation and innovation.) As for speciation, you know as well as I do that it is difficult to define. Since the ability to interbreed is often used as a definition of the broader sense of the word, and we know that different varieties of hominin interbred, it is not unreasonable to say that brain expansion does NOT constitute what you call “full speciation”. But classification is not the real issue here. The question is the potential inventiveness of the autonomous mechanism which enables brains to complexify and shrink of their own accord.

DAVID: The problem with your last sentence "sacrificing control, though he could take it again if he wished" at its basis assumes God does what He wants. God is therefore in full control.
dhw: You are clutching at semantic straws. Being able to do what he wants, and choosing to sacrifice control most of the time (i.e. allow a free-for-all) is a million miles away from being able to do what he wants and controlling every innovation, lifestyle and natural wonder in the history of evolution.
DAVID: But God is in control making your proposed choices. It is God who is making the choice!

Of course God, if he exists, makes the choice, and in my hypothesis he chooses to allow a free-for-all, which is the opposite of choosing to control everything.